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<a name="Comparisons-involving-poly_005fint"></a>
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<p>
Next: <a href="Arithmetic-on-poly_005fints.html#Arithmetic-on-poly_005fints" accesskey="n" rel="next">Arithmetic on <code>poly_int</code>s</a>, Previous: <a href="Consequences-of-using-poly_005fint.html#Consequences-of-using-poly_005fint" accesskey="p" rel="prev">Consequences of using <code>poly_int</code></a>, Up: <a href="poly_005fint.html#poly_005fint" accesskey="u" rel="up">poly_int</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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<hr>
<a name="Comparisons-involving-poly_005fint-1"></a>
<h3 class="section">10.3 Comparisons involving <code>poly_int</code></h3>

<p>In general we need to compare sizes and offsets in two situations:
those in which the values need to be ordered, and those in which
the values can be unordered.  More loosely, the distinction is often
between values that have a definite link (usually because they refer to the
same underlying register or memory location) and values that have
no definite link.  An example of the former is the relationship between
the inner and outer sizes of a subreg, where we must know at compile time
whether the subreg is paradoxical, partial, or complete.  An example of
the latter is alias analysis: we might want to check whether two
arbitrary memory references overlap.
</p>
<p>Referring back to the examples in the previous section, it makes sense
to ask whether a memory reference of size &lsquo;<samp>3 + 4<var>x</var></samp>&rsquo; overlaps
one of size &lsquo;<samp>1 + 5<var>x</var></samp>&rsquo;, but it does not make sense to have a
subreg in which the outer mode has &lsquo;<samp>3 + 4<var>x</var></samp>&rsquo; bytes and the
inner mode has &lsquo;<samp>1 + 5<var>x</var></samp>&rsquo; bytes (or vice versa).  Such subregs
are always invalid and should trigger an internal compiler error
if formed.
</p>
<p>The underlying operators are the same in both cases, but the distinction
affects how they are used.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">&bull; <a href="Comparison-functions-for-poly_005fint.html#Comparison-functions-for-poly_005fint" accesskey="1">Comparison functions for <code>poly_int</code></a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="Properties-of-the-poly_005fint-comparisons.html#Properties-of-the-poly_005fint-comparisons" accesskey="2">Properties of the <code>poly_int</code> comparisons</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="Comparing-potentially_002dunordered-poly_005fints.html#Comparing-potentially_002dunordered-poly_005fints" accesskey="3">Comparing potentially-unordered <code>poly_int</code>s</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="Comparing-ordered-poly_005fints.html#Comparing-ordered-poly_005fints" accesskey="4">Comparing ordered <code>poly_int</code>s</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="Checking-for-a-poly_005fint-marker-value.html#Checking-for-a-poly_005fint-marker-value" accesskey="5">Checking for a <code>poly_int</code> marker value</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="Range-checks-on-poly_005fints.html#Range-checks-on-poly_005fints" accesskey="6">Range checks on <code>poly_int</code>s</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="Sorting-poly_005fints.html#Sorting-poly_005fints" accesskey="7">Sorting <code>poly_int</code>s</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
</td></tr>
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Next: <a href="Arithmetic-on-poly_005fints.html#Arithmetic-on-poly_005fints" accesskey="n" rel="next">Arithmetic on <code>poly_int</code>s</a>, Previous: <a href="Consequences-of-using-poly_005fint.html#Consequences-of-using-poly_005fint" accesskey="p" rel="prev">Consequences of using <code>poly_int</code></a>, Up: <a href="poly_005fint.html#poly_005fint" accesskey="u" rel="up">poly_int</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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